Virtual Host is nothing but a cluster(s) on which the 
target application are being served. And when a virtual 
host serve one application that is called virtual hosting.
Virtual hosting is used increase the performance of 
applications.

It is nothing but host names to which weblogic server 
instances or clusters served.
Virtual hosts can be created using weblogic administrator 
console. Virtual hosting can be used to increase the 
performance of the application

A virtual host is a set of host names to which WebLogic
Server instances (servers) or clusters respond. Create
virtual hosts in order to maintain more than one server on
only one machine. Configure virtual hosts to meet your
specifications.

To create a virtual host:

   1. If you have not already done so, in the Change Center
of the Administration Console, click Lock & Edit (see Use
the Change Center).
   2. In the left pane of the console, expand Environments
and select Virtual Hosts to open the Virtual Hosts page.
   3. Click New.
   4. On the Create a New Virtual Host page, enter the name
that will identify your virtual host.

      Note: Once you create a virual host, you cannot rename
it. Instead, you must delete it and create another one that
uses the new name.
   5. Click Ok.
   6. To activate these changes, in the Change Center of the
Administration Console, click Activate Changes.
      Not all changes take effect immediately—some require a
restart

As per my views,
Virtual host is door for providing the access to an 
application. 
the same concept is also avalable on Websphere.

A Virtual Host is Host which is Virtual. You can create it 
in the same way as you create any other Virtual Host. The 
advantage of Virtual Host is same as the any other Virutal 
Host advantage.

hi Pranab, i did't get your's question . can someone plz 
explain me wot u guys are talking abt .i dono anything abt 
weblogic.

Pranab the fool is the correct guys .belive on him Kanika 
is gr8 fool

Hey Pranab,
What is your Answer Man?If You dont know,keep quite.You can 
read the correct answers.it may useful in future.Dont mind 
please.Enjoy reading!!

virtual hosting have two types 
.name based VH
  2.ip based VH
In name based VH we use one ip address and different domain 
names like 
192.168.50.103 www.xxx.com
192.168.50.103 www.yyy.com
192.168.50.103 www.zzz.com.......

this can useful redusing the band width of a network&some 
else(recommended in local system)


coming to ip based u can assign one ip address for one 
domain like

192.168.50.103 www.xxx.com
192.168.50.104 www.yyy.com
192.168.50.105 www.zzz.com

coming to weblogic VH done by using ipbased because to 
provide high performence for each application.

Virtual hosting allows you to define the host names to 
which WebLogic Server instances (servers) or clusters 
respond. When you use virtual hosting, you use DNS to 
specify one or more host names that map to the IP address 
of a server or cluster. You also specify which Web 
applications are served by each virtual host.

When one or more virtual hosts are configured, this Virtual 
Hosts page displays key information about each of them.